The physiological actions of prostaglandin (PG)F.sub.2.alpha. are mediated through interaction with the prostaglandin F.sub.2.alpha. (FP) receptor. This receptor has not previously been isolated or purified. FP-encoding DNA and the amino acid sequence of the FP receptor protein was also not known FP receptors are normally found on a wide variety of cells and tissues including the small intestine, corpus luteum, placenta, ovary, brain, myometrium, lung, kidney, stomach, muscle, eye, uterus and trachea, in humans and other animals. Binding of prostaglandin to the FP receptor protein elicits an increase in intracellular calcium levels. This signal causes the tissues to respond, for example, by muscle contraction and in the eye indirectly causes a reduction in intraocular pressure. Studies on PGF.sub.2.alpha. binding sites (FP receptors) have been performed using primarily corpus lutea tissue since PGF.sub.2.alpha. is a potent luteolytic agent Powell et al, 1974 Lancet, 1, pp 1120; Powell et al., 1974, Eur. J. Biochem., 41, pp 103-107!. Functional activities of the FP receptor have been studied using tissue preparations such as rabbit jejunum and the cat, bullock and dog iris sphincter tissues Dong and Jones, 1982 Br. J. Pharmac., 76, pp 149-155; Welburm and Jones, 1978Prostaglandins, 15, pp 287!. The above methods for studying FP receptor activities have several disadvantages in that they require tissue preparations containing several different but related receptor populations with different ligand binding properties making absolute potency and selectivity impossible. In addition, tissues contain very low levels of FP receptor and since tissue samples are required, compounds cannot satisfactorily be tested as effectors of the human FP receptor.